Healthy Living: September 4, 2018

BANGOR, Maine (WABI) – Last week there were two separate reports issued by the Maine CDC: the first described a Cumberland county resident who had tested positive for West Nile virus, and the second was a notice that West Nile virus had been isolated from a mosquito pool in Kittery. Are these stories related, or a cause for alarm? No, not really. The investigation into the case of a person testing positive concluded that the disease was most likely to have been contracted when the person was traveling in states south of Maine during the previous two weeks, because we know the incubation takes 5-15 days after the mosquito bite. The second item sounds ominous, but it was a small pool in southern Maine, and there have not been any cases linked to that discovery.


Stepping back from the concern and anxiety that can arise from these public health pronouncements, let’s look at the big picture for West Nile disease. The virus was first isolated in Uganda in 1937, and for most of the last century was the cause of isolated outbreaks in the Mediterranean basin. It is thought to have been transmitted by migrating geese to the New York’s Long Island sound area around the early 2000’s, but only rarely has been reported in Maine. Prior to last week’s report, Maine was one of three states (the others being Wyoming and Arkansas) that had no West Nile occurrences for 2018. The last Maine case in a human was in 2015. Even if someone were to contract the virus, over 70 percent of people would have no symptoms, some would have fever, headaches, and possible rash, while less than one percent would have the potentially life-threatening infection of the central nervous system known as encephalitis.

What about the risk of contracting the disease unknowingly from a blood transfusion? The good news here is that since 2003 the American Red Cross has routinely screened all donations for the West Nile infection. So the primary risk for Maine residents would be from a mosquito bite while traveling in states that do have a higher prevalence of the virus. This is another minor benefit that we can claim is related to Maine having a nice long, cold winter which kills all mosquitoes in the fall that may have harbored any virus that had traveled to Maine for a summer vacation.

Still, we should not take the risk of mosquito-borne disease too lightly. In addition to West Nile, Maine does occasionally have isolated cases of Eastern Equine Encephalitis, but even these serious infections are far more common in more southern states. And, as I had reported last year, we do not have any risk of contracting Zika here from our mosquitoes in Maine, however those traveling to Florida or the Southeast have some risk.

So what is the best advice for anyone, in Maine or otherwise, who wants to avoid mosquito bites? First, be aware that most species feed on their hosts in the early dawn or later dusk and simply avoiding being outside during these times will help. Yet there are some species, notably the salt-marsh variety that are common in coastal Maine, that have evolved the habit of all-day feeding. So the second piece of advice is to consider the use of safe insect repellent. The CDC recommends one of three possible compounds as tested to be reasonably effective and safe if used correctly:
1) DEET (N,N-diethyl meta-toluamide) has been available since the 1950’s and is best used in concentrations between 10% and 30%. It needs to be applied every 2-5 hours, and should not be used in children under 2 months. It does have a greasy feed that many dislike.
2) Picardin, is not oily and may also be used in those over 2 months. It also lasts about 2-5 hours with each application.
3) Oil of Lemon Eucalyptus. This also has been shown to be effective and has at more pleasant odor, but pediatricians do not advise its use for kids under 3 years.

Before we get too smug with our decreased risk of conditions caused by mosquitoes compared to our southerly neighbors, we do of course have our share of tick-borne disease. In addition to Lyme, we now have babesiosis, anaplasmosis, Powhassan virus, and other diseases being reported unfortunately with increased incidence in Maine. Although DEET can help, the other options above may not be as effective against tick-bite. Those who frequent conditions that harbor ticks may benefit from wearing clothing such as hats, socks or gaiters that are infused with Pyrethrin-based insecticides. Even here, however, prevention is your best option. Tick check or showering after potential exposures to these noxious pests is the stitch in time that might save nine trips to the doctor!